As Koch apologized, a former Senate staffer revealed for the first time that he had reported the relationship to the Senate's leadership in September, contradicting accounts by the leaders, who have said they first learned of the alleged affair weeks ago.

Koch resigned as majority leader last Thursday after being confronted by fellow senators about allegations of an inappropriate relationship with a subordinate. Koch never confirmed or denied the allegations at the time and has avoided interviews ever since. On Wednesday, Koch, a Republican from Buffalo, said she has caused enormous pain for the people she loves and for those she worked with.

"The events of recent days have been very difficult for me and those close to me," she said. "It is important that I spend time now focusing on the challenging days ahead as I work through some very personal issues."

Koch said when she resigned as leader that she would not seek re-election next year.

In November, Sheehan left the Senate office and took a job as a lobbyist. He would not say whether the incident prompted him to leave.

Michel, now interim majority leader, said Wednesday he and other party leaders were intentionally vague about the timeline to protect Sheehan and the other staffer who reported the relationship.

"Being specific would expose specific staff. It could reveal their identities," he said. In another conversation he said, "These whistleblowers were scared."

Michel now says he regrets not just simply refusing to disclose a timeline to reporters.

"What Cullen brought to me was stunning and unbelievable and something I didn't want to believe," said Michel, who was Koch's handpicked deputy. "Coming from Cullen, as complete as it was, I recognized, we had to take some action."

He said that at that time he consulted the Senate's human resources professionals, legal advisers, Secretary of the Senate Cal Ludeman and a group of Senate Republican leaders.

Michel said they slowly began to reach a consensus on what needed to be done.

"In order to stop a manager-employee relationship that was inappropriate, we had to act," he said. "This group put together a plan, which included what you saw last week -- a direct conversation with Senator Koch, the majority leader."

Even though Sheehan confronted Koch in September, Michel said they were concerned she took no action until senators surprised her last Wednesday at the Minneapolis Club.

"Based on Cullen's conversation [with Koch], I'd expected a different reaction from Senator Koch," Michel said. He said he hoped she would step down as majority leader but "over time, it became apparent that was not going to happen, and we would have to continue going down the road we were going down."

What's next?

Some senators have said Koch still needs to resign from the Senate, but her statement gave no hint of her plans.

Koch served as majority leader for 11 months, garnering a reputation as a thoughtful and talented leader during one of the most challenging budget deficits in recent history. A relative newcomer, Koch stunned some Senate watchers when she won the leadership post. But she had proven herself to be a gifted fundraiser and recruiter, helping ensure historic wins to give the GOP control of the Senate for the first time in nearly 40 years.

Despite Koch's assertions she didn't violate Senate rules or use taxpayer money to facilitate the relationship, the next step is unclear.

Sen. Bill Ingebrigtsen, R-Alexandria, declined to comment on Koch's statement, citing his membership on a Senate ethics panel that could investigate the incident. "I'm trying to keep myself as clean as I can here," said Ingebrigtsen, who said he had not yet seen Koch's statement. "If I'm going to make comments, it's going to taint, could potentially taint" any ethics hearing.

Dan Hofrenning, a political science professor at St. Olaf College in Northfield, said Koch's apology might not be enough to quell the drumbeat for her resignation.

"I think it was an eloquent statement, and she has gone most of the way, but I [also] think there will be some pressure on her to resign," he said.

Kathryn Pearson, a political science professor at the University of Minnesota, said Koch's ability to survive politically depends on whether there is more to the scandal.

"If this is the end of the story then, yeah, she could fill out her term as a rank-and-file member. But if there is more" that comes out, that presents an even bigger problem, she said.

Now Senate Republicans are scrambling to select a new caucus leader to guide them through the upcoming legislative session and fend off DFLers trying to regain control of the body. A new leader is scheduled to be elected Tuesday.

The president said on Twitter the agency "missed all of the many signals" sent by the suspect in the Florida school shooting and they are "spending too much time trying to prove Russian collusion with the Trump campaign."